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Theorem 19.2OLD 1700
Description: Obsolete version of 19.2 1659 as of 4-Dec-2017. (Contributed by NM, 2-Aug-2017.) (Proof modification is discouraged.) (New usage is discouraged.)
Assertion
Ref Expression
19.2OLD (xφxφ)

Proof of Theorem 19.2OLD
StepHypRef Expression
1 equid 1676 . . 3 x = x
21notnoti 115 . . . 4 ¬ ¬ x = x
32spfalw 1672 . . 3 (x ¬ x = x → ¬ x = x)
41, 3mt2 170 . 2 ¬ x ¬ x = x
5 idd 21 . . 3 (x = x → (φφ))
65speimfw 1645 . 2 x ¬ x = x → (xφxφ))
74, 6ax-mp 5 1 (xφxφ)
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wal 1540  wex 1541
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1546  ax-5 1557  ax-17 1616  ax-9 1654  ax-8 1675
This theorem depends on definitions:  df-bi 177  df-an 360  df-ex 1542
This theorem is referenced by: (None)
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